GB2416829A

GB2416829A - A heat exchange unit utilising waste water to heat cold incoming mains water

Info

Publication number: GB2416829A
Application number: GB0416965A
Authority: GB
Inventors: Wayne Kimberlin; Darren Woodcock; Simon Fawcett; Allen Green; Keith Williams; George Jones
Original assignee: A K IND Ltd
Current assignee: A K IND Ltd
Priority date: 2004-07-29
Filing date: 2004-07-29
Publication date: 2006-02-08
Anticipated expiration: 2024-07-29
Also published as: GB2416829B; GB0416965D0

Abstract

A heat exchange unit 10 for heating cold incoming mains water comprises a casing 40 communicating waste fluid that is in heat exchange relationship with the incoming mains water, which also passes through the casing. Waste water communicates via a waste outlet 13 and connecting pipe 14 to pass over a heat transfer element 20 disposed inside the casing 40. The casing 40 may have a weir (48, fig 4) with a well (51) which receives pipe 14 so that it functions as a u-bend water trap. The incoming mains water may enter the casing 40 at lower position that which it exits (fig 6) and may flow in an opposite direction to the waste water. Heat exchange unit 10 may located underneath a shower tray 11 or may be integral with the tray, a bath tub or domestic appliance casing. The heated mains water may be supplied to an electric shower, a mixer shower using water from hot water cylinder, a bath, a dishwasher or washing machine.

Description

241 6829

HEAT EXCHANGER ASSEMBLY AND APPLIANCE INCLUDING HEAT

EXCHANGER

The present invention relates to heat exchangers, in particular heat exchangers for heating water supplied to an appliance, and to an appliance including a heat exchanger.

It is common for appliances, particularly household appliances that use or provide hot water, to be supplied with cold water which is then heated by the appliance itself.

For example, electric showers have become increasingly popular as they can provide cheaply hot water on demand and do not require the provision of a large hot water tank.

Electric showers are typically connected only to a cold water supply and include a heating unit to heat the water to a chosen temperature.

A problem with existing electric showers is that their efficiency is heavily lO dependent on the pressure and the temperature of the incoming water. If the water arriving from the mains is very cold (for example, as it might be in winter), more energy or time is required to heat the water to the desired temperature. Typically, this results in variable water flow.

Similar problems arise with other appliances, including dishwashers, washing machines and so on.

The present invention seeks to provide improved appliance operation.

According to an aspect of the present invention, there is provided a system for heating fluid including a casing, a waste fluid connector for connecting the system to a waste of an appliance, an inlet fluid connector for connecting an incoming fluid supply to the system, and a heat exchanger within the casing and including a recovery portion through which waste fluid can pass to recover heat energy from such waste fluid and a heat transfer portion through which incoming fluid can pass and to which recovered heat energy can be transferred to such incoming fluid.

Such a system allows heat from warm waste fluid to be transferred to cold incoming fluid, thereby pre-heating it before its use. This can help reduce energy wastage and can reduce the amount of energy required by an appliance using in effect preheated incoming fluid to heat that fluid up to the desired temperature. The system can be particularly useful in an electric shower of the type described above, in which by virtue of preheating the mains water supply can reduce or otherwise mitigate the disadvantages mentioned above. It is similarly useful for any appliance which heats up cold mains water or other fluid.

Advantageously, the heat recovery portion is in use oriented substantially horizontally, in which case the waste fluid connector is preferably substantially orthogonal to the heat recovery portion. This arrangement allows waste fluid to spread across the heat recovery portion to enhance heat recovery.

In the preferred embodiment, the heat transfer portion provides a chamber through which inlet fluid can flow, the chamber being arranged in use such that incoming fluid enters the chamber at a lower position than that at which it exits the chamber. This ensures that the incoming fluid fills the chamber to maximise heat transfer from the waste fluid.

In a preferred embodiment, the system includes a fluid valve or U-bend between the waste fluid connector and the heat recovery portion. This provides the same function as a traditional U-bend used in sanitary and other appliances.

Advantageously, the fluid valve includes a recess formed within the casing. In one embodiment, a waste tube from an appliance can be located in the recess so as to form the U-bend valve. Alternatively, the system could be provided with a preformed U-bend with a coupling to couple to a waste pipe outside the casing. Preferably, the casing provides a downward flow path for waste fluid such that waste fluid is drained substantially completely from the system. Advantageously, the waste fluid flow path is in a direction opposite to the flow path of incoming fluid.

In an embodiment, the system is integral with an appliance. For example, the system may be integral with a shower tray, a bath tub, or other domestic appliance casing.

According to another aspect of the present invention, there is provided an appliance including a system as specified herein.

In the preferred embodiment, the appliance is a domestic appliance. With such an assembly, more efficient heating of incoming fluid and recycling of the heat in waste fluid can improve the performance of such appliances, can reduce the amount of electricity used and thus can result in lower electricity bills.

Preferably, the appliance has a heating element for heating incoming fluid which has been preheated through the system. Advantageously, the appliance may be an electric shower, a bath, a dishwasher, a washing machine. The invention is applicable to any appliance which heats incoming fluid to operate, particularly incoming fluid derived solely form a cold mains supply.

Preferably, the appliance uses incoming fluid and produces waste fluid substantially simultaneously. In such an arrangement, heat from waste fluid can be most efficiently transferred to incoming fluid.

In the case where the appliance is a shower, the heat exchanger is preferably integral with the shower tray. This allows the heat exchanger to be discretely located and can reduce the space requirements of the system.

According to another aspect of the present invention, there is provided a method of preheating incoming water for an appliance including the steps of providing a system as specified herein, passing waste fluid from the appliance through the recovery portion, and passing incoming fluid to the heat transfer portion so as to heat said incoming fluid.

Advantageously, the method includes the step of feeding the heated incoming fluid to a fluid outlet of the appliance. Preferably, incoming fluid is preheated by said system and the method includes the step of heating the preheated incoming fluid prior to the fluid outlet.

Preferred embodiments of the present invention are described below, by way of example only and with reference to the accompanying drawings, in which: Figure l is a schematic drawing of an embodiment of system and appliance incorporating such a system; Figure 2 is a schematic representation of the system of Figure 1; Figure 3 is a diagram of a heat exchanger of the system of Figures 1 and 2; Figure 4 is a perspective view of the casing of the system of Figure 1; Figure 5 is a perspective view from another angle of the casing of Figure 4; Figure 6 is a perspective view of the casing of Figure 4 with the heat exchanger of Figure 3 fitted therein; Figure 7 is a perspective view of a cover and the casing of Figures 4 and 5; Figure is a perspective view from another angle of the cover and casing of Figure 7; Figure 9 is a schematic drawing of another application of the system of Figure 1; and Figure 10 is a perspective view of an alternative embodiment of heat exchanger for the system of Figures 1 and 9.

The principal embodiment described below is related to a system for a domestic electric shower. However, the skilled person will readily appreciate the application of those teachings to a system for other uses, such as baths, dishwashers, washing machines and so on.

Referring to Figure 1, there is shown an embodiment of system used with a domestic electric shower. The embodiment of heat exchanger system 10 shown is provided with a casing 40 and is located underneath shower tray 11 and coupled to waste outlet 13 of the shower tray via connecting pipe 14 into the body of the device 10. A drain outlet pipe 15 is provided for drainage of waste fluid from the shower tray 11, after passing through the device 10.

The device 10 is provided with a heat exchanger transfer element 20, described in more detail below, which includes an inlet coupling conduit 23 and an outlet conduit 24.

The inlet conduit 23 is coupled to a cold water mains supply through a check valve 16.

The outlet conduit 24 is coupled to an inlet of an electric shower unit 17 of electric shower 12. The shower unit 17 is provided with an electric heating element for heating water fed thereto.

Figure 2 illustrates schematically heat exchanger device 10, showing an embodiment of heat transfer exchanger 20 within the casing 40. In this embodiment, the heat exchanger 20 is a thin hollow structure which provides a labyrinth path therein by means of bames extending within the volume of the structure extending orthogonally to the plane of the structure. The inlet conduit 23 coupled directly into the interior of the heat exchanger and passes through an aperture in the casing 40 and in use is coupled to a cold mains water supply. The outlet conduit 24 is located at the other end of the heat exchanger 20, the conduit 24 passing through an aperture in the casing 40. The casing also provides, in this embodiment, the waste inlet conduit 14 and the waste outlet conduit 15, these being integrally formed in the casing 40.

Referring to Figure 3, in the preferred arrangement of heat transfer exchanger 20, the inlet and outlet have formed integrally with the exchanger upstanding coupling tubes or bosses 31, 32 for coupling to the inlet and outlet tubes 23, 24 respectively.

Referring now to Figures 4 and 5, these show the preferred embodiment of casing 40. The casing 40 is preferably fabricated from a plastics material and is generally rectangular in shape and of suitable dimensions to comfortably house heat transfer element 20 and to fit under a bath or shower tray 11. Casing 40 has a base wall 41, which has two parts that slope downwardly and towards each other. Where they meet a channel is formed, which slopes towards drain outlet pipe 15 in end wall 43 of housing 40. Along the lower part of side walls 44, 45 and end wall 46 of housing 40, there is situated a sloped shelf 47 upon which heat exchanger 20 is able to sit.

At one end of housing 40, next to end wall 43, there is positioned a weir 48.

Weir 48 includes an outlet port 49 coupling the interior chamber 50 to drain outlet pipe 15. Weir 48 also includes a well 51 and an overflow wall 52.

The exterior side surfaces of the casing 40 are provided with fixtures 54 for housing spirit levels and fixtures 55 for supporting levelling feet (not shown). Lugs 56 are also provided for securing in place a lid 70, described in further detail below.

Heat exchanger 20 is designed to rest on the sloped shelf 47, abutting weir 48 at one end and the walls 44 and 45 at its other two edges but does not abut wall 46, thereby to leave a gap for waste fluid to flow down onto base wall 41. The sides of housing 40 have indentations 53 through which the inlet and outlet pipes to and from the exchanger can pass.

Figure 6 shows housing 40 (fixtures 54, 55 and lugs 56 omitted for clarity) with the heat exchanger 20 in place. It can be seen that the heat exchanger 20 lies at an angle, so that cold water from the mains enters through port or boss 31, moves upwards through the heat exchanger to exit through port or boss 32.

Figures 7 and 8 show cover 70 which fits onto the base portion of the casing 40.

Heat exchanger 20 is omitted for the purposes of clarity. Support struts 71 are of increasing length from one end of the lid to the other so that they are able to rest on the edges of heat transfer element 20 along the slope in which it rests, thereby holding it in place.

Inlet pipe 14, which connects heat exchanger lO to waste outlet 13 of shower tray 11, extends through lid 70. It is arranged to extend into well 51, such that together well 51 and inlet pipe 14 form a U-bend. Thus, it is not necessary to provide a separate U bend with a shower or other appliance.

In use, when shower 12 is switched on, cold water from the mains is drawn through single check valve 16 and through heat exchanger 20 before being heated by heating unit 17. Warm waste fluid from shower 12 leaves shower tray 11 via waste outlet 13. Rather than being fed directly to the drain, the warm waste fluid passes into the housing 40 of heat exchanger assembly 10 through the inlet pipe 14. The waste fluid first passes through the U-bend formed by the tube 14 and well 51, then over weir 48 and over the upper surface of heat exchanger O and eventually to the base 41 of the case 40 through appropriate passages (not shown). When the waste fluid reaches base 41, the slope of base 41 allows the waste to flow out through port 49 and drain outlet pipe 15.

The difference in temperature between the warm waste fluid flowing over the heat exchanger 20 and the cold mains water in the heat exchanger allows heat to be transferred from the waste to the cold mains water. This results in the mains water exiting heat exchanger assembly 10 at a higher temperature than when it entered, and reduces the energy required by heating unit 17 to heat the water to the desired temperature for showering.

The overflow 52 allows direct flow of waste shower fluid to the drain pipe 15 in the case that the path over heat exchanger 20 become blocked or when the fluid flow is above a predetermined flow.

There are various advantages of the above-described arrangement.

The positioning of heat exchanger assembly 10 underneath shower tray 11 allows inlet pipe 14 to be as short as possible. This means that the waste water retains as much of its heat as possible before coming into contact with heat exchanger 20.

Fabricating heat exchanger 20 from stainless steel or copper allows efficient transfer of heat from the warm waste fluid to the cold mains water. Moreover, stainless steel is rust-resistant, and therefore heat exchanger 20 is protected from the damaging effects of prolonged contact with water.

The casing 40 is preferably made from a plastics material, which is heat insulating and normally has a longer life span. This minimises heat loss from the waste fluid to the environment and can help increase the amount of heat energy from the waste fluid which is transferred to the mains water in heat exchanger 20.

Sloping base 41 ensures that waste water is efficiently removed from the assembly 10 once it has flowed over the heat exchanger 20. The positioning of heat exchanger 20 in the sloping manner shown ensures that the mains water fills the heat exchanger cavity, thereby to maximise heat transfer from the waste fluid. The fixtures 54 for spirit levels and fixtures for levelling feet 55 enable the user to ensure that heat exchanger 10 is placed level. The skilled person will appreciate that the heat exchanger 20 can be made from any suitable heat-conducting material that is able to resist prolonged contact with water. It could also have any arrangement that serves to create a longer path for the incoming water to flow through, providing more time for heat transfer.

Other arrangements for the inlet pipe 14 and outlet pipe 15, and bosses 31, 32 will also be readily apparent to the skilled person.

Although ideal for electric showers, the heat exchanger assembly can also benefit conventional mixer showers using hot water from a domestic hot water cylinder. There are two possible benefits from the assembly, arising when the pre-heated water enters the shower: (a) if shower temperature and flow rate remains constant at the shower outlet, then less energy will have been used to heat the water thus saving energy (electricity); and (b) if the same amount of energy (electricity) is used in the shower then the result would be a better flow rate through the shower, a warmer shower or a combination of the two.

The heat exchanger assembly 10 could be formed integrally with the shower tray 11 instead of being provided as a separate unit, in which case at least a part of the casing 40 could be formed as a part of the shower tray 11.

Referring now to Figure 9, there is shown another embodiment of application of the system taught herein, namely with a bath tub. The heat exchanger assembly 10 is fitted under the bath tub 90 and a shower attachment 17 is provided to enable showering within the bath tub 90. In this arrangement heat exchanger 10 is connected in series with tap 91 of bath tub 90 as well as with the heating unit of the shower 17. The mains water supplies to the bath and to the shower are provided downstream of the heat exchanger assembly 10, which ensures that the heat exchanger 20 can be flushed by mains water when a bath is taken instead of a shower.

The above-described system can be used with any appliance that uses or provides a hot fluid. For example, it could be located so that cold water being supplied to a hot water tank passes through the heat exchanger assembly 10. The incoming water could be pre-heated by waste fluid from a bath or shower.

Other examples include use with a washing machine or a dishwasher, where the water inlet, which is also typically the mains cold water supply, is heated by waste fluid from the appliance prior to supply to the appliance itself.

Although it is preferred that the system is used to recover heat energy lost by the appliance it warming water the appliance itself uses, this is not strictly necessary. For example, the water which is preheated to be used in other applications, in which case the outlet from the heat exchanger 20 is fed to another appliance.

An alternative embodiment of heat exchanger is illustrated in Figure 10. In this embodiment, instead of a pair of plates forming a cavity in which there are located a plurality of dames, the heat exchanger 20' is formed as an array of connected pipes 101.

A plurality of pipes 101 are provided in parallel adjacent one another and connected at respective ends to an inlet pipe 23 and an outlet pipe 24 Thus, water fed into the inlet pipe 23 flows through the pipes 101 and then into the outlet pipe 24. Of course, with such an arrangement, water is provided with a plurality of paths of different length in the heat exchanger 20'. Another embodiment is as shown in Figures 1 and 9, in which the heat exchanger provides a tube in a serpentine path from passage of mains water therethrough.

The features of the various embodiments and modifications may be interchanged and/or combined as appropriate.

Claims

1. A system for heating fluid including a casing, a waste fluid connector for connecting the system to a waste of an appliance, an inlet fluid connector for connecting an incoming fluid supply to the system, and a heat exchanger within the casing and including a recovery portion through which waste fluid can pass to recover heat energy from such waste fluid and a heat transfer portion through which incoming fluid can pass and to which recovered heat energy can be transferred to such incoming fluid.

2. A system according to claim 1, wherein the heat recovery portion is in use oriented substantially horizontally.

3. A system according to claim 2, wherein the waste fluid connector is preferably substantially orthogonally to the heat recovery portion.

4. A system according to claim 1, 2 or 3, wherein the heat transfer portion provides a chamber through which inlet fluid can flow, the chamber being arranged in use such that incoming fluid enters the chamber at a lower position than that at which it exits the chamber.

5. A system according to any preceding claim, including a fluid valve or U-bend between the waste fluid connector and the heat recovery portion.

6. A system according to claim 5, wherein the fluid valve includes a recess formed within the casing.

7. A system according to claim 6, wherein a waste tube from an appliance can be located in the recess so as to form the U-bend valve.

8. A system according to claim 6, wherein the system is provided with a preformed U-bend with a coupling to couple to a waste pipe outside the casing.

9. A system according to any preceding claim, wherein the casing provides a downward flow path for waste fluid such that waste fluid is drained substantially completely from the system.

10. A system according to any preceding claim, wherein the waste fluid flow path is in a direction opposite to the flow path of incoming fluid.

11. A system according to any preceding claim, wherein the system is integral with an appliance.

12. A system according to claim 11, wherein the system is integral with a shower tray, a bath tub, or other domestic appliance casing.

13. An appliance including a system according to any preceding claim.

14. An appliance according to claim 13, wherein the appliance is a domestic appliance.

15. An appliance according to claim 13 or 14, wherein the appliance has a heating element for heating incoming fluid which has been preheated through the system.

16. An appliance according to claim 13, 14 or 15, wherein the appliance is an electric shower, a bath, a dishwasher, a washing machine.

17. An appliance according to any one of claims 13 to 16, wherein the appliance uses incoming fluid and produces waste fluid substantially simultaneously.

18. A method of preheating incoming fluid for an appliance including the steps of providing a system as specified herein, passing waste fluid from the appliance through the recovery portion, and passing incoming fluid to the heat transfer portion so as to heat said incoming fluid. Advantageously, the method includes the step of feeding the heated incoming fluid to a fluid outlet of the appliance. Preferably, incoming fluid is preheated by said system and the method includes the step of heating the preheated incoming fluid prior to the fluid outlet.

19. A system for heating fluid substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.

20. An appliance including an integral heat exchanger substantially as hereinbefore described with reference to and as illustrated in the accompanying drawings.